Duct leakage testing puts the duct system under pressure and measures how much air escapes. We seal the registers, connect a calibrated fan to the system, bring it to a set pressure, and read how much air the fan has to push to hold that pressure. Whatever the fan has to supply is exactly what the ductwork is losing through seams, boots, connections and tears.

Here is why anybody should care. In a Florida house the ducts usually run through the attic, and a Freeport attic in July is punishingly hot and full of humid outdoor air. Air lost from a supply duct up there is air you already paid to cool, dumped into a space nobody occupies. Worse, a leaky return pulls that hot attic air straight into the system, so the equipment spends its day cooling the attic instead of your bedrooms.

The test turns a hunch into a number. Instead of arguing about whether the ductwork is bad enough to justify repairs, you get a measured leakage figure against the system’s design airflow. That number tells you plainly whether sealing is worth doing and gives you something to compare against after the work is finished.

Flex duct is joined with mastic, tape and straps at boots, takeoffs and plenum connections. Those joints are the failure points. Tape dries out and lets go, straps loosen, a boot works free of a ceiling register, and an insulated flex run gets torn by somebody moving through the attic to service something else. None of it is visible from inside the house.

Heat and humidity accelerate all of it. An attic here swings through wide temperature ranges every single day for months, and materials expand, contract and get brittle. Meanwhile our high dew points mean that when air leaks around a cold supply boot, the surrounding surfaces sit below dew point and condensation forms. That wets insulation, stains ceilings, and gives mold something to live on.

Return side leaks deserve special mention because they do the most damage for the least visibility. A return that pulls unconditioned attic air is importing hot, humid, dusty air directly into your filter and coil. You feel it as a house that never dehumidifies properly and a filter that loads up far faster than it should.